1. Field of Invention
The present invention relates to a method and apparatus for positioning semiconductor pellet in a die bonding apparatus, tape bonding apparatus, bump bonding apparatus or the like.
2. Prior Art
In a die bonding apparatus, tape bonding apparatus, bump bonding apparatus or the like, a semiconductor pellet is removed from a tray or wafer and placed on a positioning stage, and once placed on this positioning stage, the semiconductor pellet is positioned by a positioning claw. After this, in a die bonding apparatus, the semiconductor pellet is bonded to a lead frame. In a tape bonding apparatus, the semiconductor pellet is bonded to a carrier tape. In a bump bonding apparatus, a bump is formed on an electrode of the semiconductor pellet. In other words, in these bonding apparatuses, the semiconductor pellet is positioned prior to bonding or the formation of a bump.
Operations in these bonding apparatuses will be described below in more detail.
As shown in FIG. 5, a die bonding apparatus has a positioning stage 51 for holding a semiconductor pellet 50 by means of a suction hole 51a, a positioning claw 52 for positioning the semiconductor pellet 50 on the positioning stage 51, a frame feeder 54 for conveying and positioning a lead frame 53, and a bonding device 60 for bonding the semiconductor pellet 50 to the lead frame 53. The positioning claw 52 is provided on an XY table 55 which is driven in the X and Y directions. In the bonding device 60, a bonding head 62 is mounted on an XY table 61 that is driven in the X and Y directions, and a bonding arm 63 is provided on the bonding head 62 so as to be moved up and down. A bonding tool 64 is provided on the distal end of the bonding arm 63. This bonding tool 64 is in the form of a suction nozzle that holds the semiconductor pellet 50 by suction.
This type of die bonding apparatus is disclosed in, for instance, Japanese Patent Application Laid-Open (Kokai) Nos. H4-61241 and H4-312936.
When the semiconductor pellet 50 is placed on the positioning stage 51, it is held by suction on the positioning stage 51. Then, the XY table 55 is driven to move the positioning claw 52 toward the semiconductor pellet 50, and the semiconductor pellet 50 is positioned by the positioning claw 52. Next, the XY table 61 of the bonding device 60 is moved in the Y direction so as to be above the semiconductor pellet 50 on the positioning stage 51, and the bonding tool 64 is lowered to hold the semiconductor pellet 50. The bonding tool 64 is then raised, moved to above the bonding position of the lead frame 53, and then lowered, thus bonding the semiconductor pellet 50 to the lead frame 53.
As to a tape bonding apparatus, and particularly an inner lead bonding apparatus, it is structured, as shown in FIG. 6, more or less the same as the die bonding apparatus shown in FIG. 5. In this inner lead bonding apparatus of FIG. 6, however, the positioning claw 52 does not move; and instead the positioning stage 51 is mounted on the XY table 55, and the positioning stage 51 is moved to beneath a carrier tape 65 by the XY table 55. Also, the bonding tool 64 is not a suction nozzle and is shaped such that a lead provided on the carrier tape 65 will be pressed against the semiconductor pellet 50.
Japanese Patent Application Laid-Open (Kokai) No. H2-244735 discloses this type of tape bonding apparatus.
When a semiconductor pellet 50 is placed on the positioning stage 51, it is held by suction on the positioning stage 51. The XY table 55 is driven to move the positioning stage 51 toward the semiconductor pellet 50, and the semiconductor pellet 50 is positioned by the positioning claw 52. The XY table 55 is then driven to move the positioning stage 51 to beneath the carrier tape 65, after which the lead of the carrier tape 65 is pressed against and bonded to the semiconductor pellet 50 by the bonding tool 64 of the bonding device 60.
As to a bump bonding apparatus, it is also, as shown in FIG. 7, structured more or less the same as the die bonding apparatus shown in FIG. 5. In this bump bonding apparatus, however, the positioning stage 51 doubles as a bonding stage, and a wire bonding device is used as the bonding device 60. Therefore, a very fine (20 to 30 xcexcm) wire of gold or solder (not shown) is passed through the bonding tool 64.
When the semiconductor pellet 50 is placed on the positioning stage 51, it is held by suction on the positioning stage 51. The XY table 55 is driven to move the positioning claw 52 toward the semiconductor pellet 50, and the semiconductor pellet 50 is positioned by the positioning claw 52 provided on the XY table 55. A bump is then formed on an electrode of the semiconductor pellet 50 by the bonding device 60. In this bump formation method, a ball formed at the distal end of the wire passing through the bonding tool 64 is pressed against the electrode of the semiconductor pellet, the wire is cut at the base of the ball, and a bump is formed on the electrode of the semiconductor pellet.
An example of this type of bump bonding apparatus can be found in Japanese Patent Application Laid-Open (Kokai) No. H7-86286.
In the above bonding apparatuses, the semiconductor pellet 50 is moved by the positioning claw 52 during the positioning process; accordingly, it is necessary that the positioning stage 51 holds the semiconductor pellet 50 with a weak suction force that allows the semiconductor pellet 50 to be moved. However, since the semiconductor pellet 50 is kept held by this weak suction force in the above bonding apparatuses, there is the danger that the semiconductor pellet 50 is misaligned due to vibration or other reasons as described below.
More specifically, in the die bonding apparatus shown in FIG. 5, the semiconductor pellet 50 positioned by the positioning claw 52 is moved over the lead frame 53 by being held by the bonding tool 64; accordingly, much of a problem would not occur. In the case of the tape bonding apparatus shown in FIG. 6, however, the positioning stage 51 and the semiconductor pellet 50 held thereon are moved to beneath the carrier tape 65; accordingly, the semiconductor pellet 50 is susceptible to misalignment during this movement. In addition, in the case of the bump bonding apparatus shown in FIG. 7, since the formation of the bump is performed by the bonding device 60 on the semiconductor pellet 50 held on the positioning stage 51, the semiconductor pellet 50 is susceptible to misalignment during this bump formation.
Accordingly, it is an object of the present invention is to provide a semiconductor pellet positioning method and apparatus that prevent the misalignment of a semiconductor pellet once it has been positioned.
The method of the present invention for accomplishing the above object is a semiconductor pellet positioning method in which a positioning stage for holding a semiconductor pellet is moved relative to a positioning claw, and the semiconductor pellet is positioned by the positioning claw; and in the present invention during the positioning of the semiconductor pellet, the semiconductor pellet is held on the positioning stage by a suction force that is weak enough so that the positioning claw can move the semiconductor pellet, and upon completion of the positioning, the semiconductor pellet is held on the positioning stage by a suction force that is stronger than suction force used during the positioning.
The apparatus of the present invention for accomplishing the above object is a semiconductor pellet positioning apparatus that comprises a positioning stage for holding a semiconductor pellet and a positioning claw for positioning the semiconductor pellet by moving relative to this positioning stage; and in the present invention, a suction force control means is further provided so that the semiconductor pellet is held on the positioning stage during the positioning of the semiconductor pellet by a suction force that is weak enough so that the positioning claw can move the semiconductor pellet and that upon completion of the positioning the semiconductor pellet is held on the positioning stage by a suction force that is stronger than the suction force used during the positioning.